The present invention relates to foam compositions containing a systemic pesticide or herbicide, a process for their production and to a method for applying them.
Agricultural chemicals such as herbicides and pesticides have been applied by a variety of techniques. One technique which has been found to be particularly advantageous is the incorporation of the agricultural chemical into a foam or a foam-forming composition because application in this manner reduces the loss of such chemicals due to wind drift. The application of foams is also more controllable than spraying of liquids and waste due to application in an unintended area is substantially reduced.
It has generally been assumed that long lasting foams are particularly desirable because the insecticide or herbicide would be released at a controlled rate for a prolonged period of time.
A small scale example of such foam compositions is seen in U.S. No. 3,524,911 which teaches aerosol insecticidal compositions. The disclosed compositions are suitable for use on relatively small areas but are impractical for application to large fields of crops.
U.S. No. 3,689,245 discloses agricultural pesticides which are dispersed or dissolved in an aqueous alkali metal silicate foam. These foams are said to expand to a volume of from 3 to 300 times the volume of the liquid in the foam. The alkali metal silicate content of the foam is from 5 to 50% by weight. The pesticide is present in an amount of from 0.1 to 25% by weight of the foam.
U.S. Nos. 3,713,404 and 3,922,977 disclose the use of high expansion foams (i.e., foams which expand the volume of the liquid stream of the foam-providing solution at least 80 fold) as vehicles for applying needs fertilizers and other biological agents such as insecticides and herbicides. These foams which are taught to be stable for periods of from 10 to 30 minutes are generated from a concentrate which is passed through a garden hose having a minimum water pressure of at least 15 psi. The concentrate is composed of (a) a foaming agent selected from water soluble salts of lauryl ether sulfate, water soluble salts of lauryl sulfonates, fatty acid esters of sodium isetheonate and mixtures thereof; (b) a foam enhancer selected from a specified group of compounds; (c) a foam stabilizer selected from a specified group of glycols and alcohols; (d) a foam-providing composition fluidity modifier selected from a specified group of alcohols; and (e) a plant agent such as a herbicide or insecticide.
U.S. No. 4,086,331 discloses gelatin-based foam compositions which may be applied as a protective covering. These foams composed of gelatin, anionic surface active agent, and a water soluble ferrous salt are relatively long lasting. These foams are very sensitive to temperature changes.
The use of whey solids as agricultural foam stabilizers is addressed in Lambou et al, "Whey Solids as Agricultural Foam Stabilizers", J. Agr. Food Chem., Vol. 21, No. 2, 1973. The foams disclosed therein persisted for a minimum of 6 hours.
However, long lasting foams do not completely resolve the problem of wind drift. In fact, the foams themselves will be subject to drifting. McCall et al evaluated several low expansion foams as possible carriers for herbicides in their work reported in "Influence of Foam Adjuvants on Activity of Selected Herbicides", WEED SCIENCE, Vol. 22, Issue 4 (July), 1974. The foam adjuvants used in this study were (1) alpha-(p-alkylphenyl)-omega-hydroxypoly(oxyethylene) sulfate; (2) a mixture of alpha-alkyl-omega-hydroxypoly(oxyethylene)sulfate, 1,3-propanediol and coconut fatty acid; and (3) a mixture of alcohol sulfates, salts of alkyl and dialkyl 2,4-diketotetra-hydrofuran, alkyl sulfonates and isopropanol.